Tuesday, 2 August 2011

It doesn’t take a scientist, sports or other, to tell you that men and women are different. However, it was really only recently that kit manufacturers noticed this difference in the area of sports shoe design.

A woman’s foot is 3-4% narrower than men’s - this is particularly manifest at the rear.

Shoe implications

Manufacturers need to create a specific ‘last’ for their shoes. A last determines the way the shoe is manufactured and the way the relevant pattern making machines are set up.

Women are more prone to getting bunions compared to men

Shoe implications

Some sportswear brands such as adidas incorporate a soft and flexible insert in the shoe’s upper to reduce the friction that could lead to bunions developing.

Women’s feet are more flexible compared to men’s

Shoe implications

Women’s running shoes should be more flexible (but supportive and provide the ‘right’ control of foot-strike – see anthropometrical differences). Often their shoes will have a different tread configuration to allow the female foot to flex in its particular way. For example, in adidas shoes a thinner torsion ™ system bar and additional grooves in mid-foot add to the shoe’s woman-friendly flexibility.

In the illustration below you will see two adidas shoes and their different sole configurations. Notice the pattern (green) on the woman’s (right hand) shoe – this is designed to create greater flexibility.

Women’s running style

Women because they are generally lighter than men do not generate such high impact forces – see graph below

Women runners exhibit less running forces

Because women do not generate as high impact forces as men on foot-strike they require less cushioning in their shoes. This can result in their running shoes having 21% less rear-foot cushioning and 24% forefoot cushioning.

Women runners have a different foot-strike compared to men

Women strike the ground with a much shallower angle (from heel to toe) compared to men and their feet tend to be less splayed compared to men. This is known as a ‘less exorated’ landing – putting it into everyday language women’s feet tend to strike the ground with their feet pointing forward at 12 o’clock, whilst men tend to strike the ground at a more ‘10 to 1 o’clock’ position.

Shoe implications:

The different landing foot-strike angles require different heel bevel construction in running shoes. In a woman’s shoe it is more rotated to control their landing – see illustrations below.

Anthropometrical differences

The ‘Q angle’

Women’s lower body shape creates greater and different forces on their knees and ankles compared to men. This is largely the result of their wider hips and the inward angle of their thigh bone (the femur which extends from the pelvis to the knee). This is known as the ‘Q angle’.

Greater knee forces

The increased angular forces on the knee also create greater forces on it which could increase injury risk.

Running and knee injuries

As well as the Q angle other factors such as hamstring and quadriceps muscle flexibility, quadriceps strength, weekly mileage and weight can also influence whether a runner is more predisposed to injury. American researchers evaluated these (and other factors) in 20 runners (13 females and 7 males) ranging in age from 20–55. Specifically they were interested in the extent of the forces that the participant’s knees were subject to whilst running. It’s the often the case that the greater these forces the greater the risk of knee injury. The team discovered that the key factors in terms of increased knee forces were, not surprisingly, greater weekly mileage, poor hamstring flexibility, greater body weight and perhaps less obviously increased quadriceps strength. Greater quadriceps strength needs further explanation as this could be considered a positive and not a negative. In actual fact what matters in particular is the ratio of strength between the hamstrings and the quadriceps. Women tend to have weaker hamstrings when compared to men; this can ‘enhance’ the dominance of the quads in the running action – which due to their anthropomorphic considerations can increase the forces that their knees are subject to. It’s therefore recommended that women (and men) strengthen their hamstrings with relevant weights and body weight exercises (and improve these muscles’ flexibility). In doing so the forces to which the knee is subject can be reduced. Returning to the thoughts of the researchers, they believed that most of these risk factors could be altered to reduce injury potential.

PFPS (patellofemoral pain syndrome) is more commonly known as ‘runner’s knee’. Pain is normally felt on the outside of the knee and comes on after 20 minutes of running

Implications for shoes

Women tend to run with an over-pronated gait. Over-pronation means that the foot turns too much inward on foot-strike from the body’s centre line. This means that, depending on the degree of pronation, a shoe needs to be either a motion control or a support one. Pronation can lead to an increased injury risk.

Shoes can be designed to reduce the forces that the knees are subject to – for example adidas shoes have a technology called ‘formotion™’ – which is positioned at the heel which control pronation and therefore knee loading.

As can be seen from the above research and information, it is definitely not a case of ‘one size fits all’ when it comes to choosing the right running shoes based on your gender. There are myriad factors that that make the requirements of women’s shoes different to men’s and shoe companies are investing heavily in relevant technologies and research.